Box lock surgical instrument and method of its manufacture

ABSTRACT

By electrically fusing a pin between the outer elements of a box hinge, and thereafter performing the hardening step, stresses which tend to cause instrument failures after a period of use are eliminated. Even if the pin fractures during use, the fact that it is fused to the outer elements of the box hinge prevents broken-off parts of the pin from falling out of the instrument.

UNITED STATES PATENTS 12/1942 Grubel 76/104 A United States Patent 1 13,911,766 Fridolph et al. Oct. 14, 1975 [54] BOX LOCK SURGICALINSTRUNIENT AND 2,611,288 9/1952 Schifibauer 81/416 METHOD OF ITSMANUFACTURE 2,939,214 7/1960 Andersson et a1. 76/104 R 3,209,753 10/1965Hawkins et al. 128/321 [75] In n s: J Fridolph, m, 3,459,187 8/1969Pallotta 76/104 R Robert W. Wilson, Dresher; Rodney 3,763,726 lO/ 1973Hildebrand 81/416 J. Kulp, Harleysville, both of Pa.

[73] Assignee: Pilling Co., Fort Washington, Pa. Primary Examiner HinsonAttorney, Agengor FirmSmith, Harding, Earley & [22] Filed: May 15, 1974Follmer [21] Appl. No.: 469,967

[57] ABSTRACT [52] Cl 76/101 R; 7 By electrically fusing a pin betweenthe outer elements of a box hinge, and thereafter performing the harden-[51] B211; 9 6 ing step, stresses which tend to cause instrument fail-[58] d 0 Sean 0 4 ures after a period of use are eliminated. Even if theB2 1 pin fractures during use, the fact that it is fused to theReferences Cited outer elements of the box hinge prevents broken-offparts of the pin from falling out of the instrument.

6 Claims, 11 Drawing Figures US. Patent Oct. 14, 1975 Sheet 1 of 23,911,766

US. Patent Oct. 14, 1975 Sheet 2 of2 3,911,766

HIIH H III FIG. ll.

BOX LOCK SURGICAL INSTRUMENT AND METHOD OF ITS MANUFACTURE BACKGROUND OFTHE INVENTION This invention relates to surgical instruments, andparticularly to the so-called box lock instruments. Instruments such asforceps, hemostats, and clamps are often provided with box lock jointsparticularly where a high degree of reliability and the very accuratemeeting of grasping members is required.

The box lock joint is a special hinge used in instruments of the typecomprising first and second members each having, at one end, operativemeans such as a clamping or gripping jaw adapted to cooperate with theoperative means of the other member, and each having at its opposite endmanipulable means, typically a ring handle, for controlling the movementof the operative means on the same member. The first member has abifurcated portion at an intermediate location whereby its operativemeans and its manipulable means are connected by two separate elementshaving a slot between them. The second member extends through the slotwith its operative means and its manipulable means on opposite sides ofthe bifurcated portion of the first member. A pin, extending across theslot and through a hole in the portion of the second member within theslot, completes the hinge and allows the operative means to becontrolled by the manipulable means for clamping, depending on thenature of the particular instrument. The box lock joint is generallypreferred because of its strength, the low degree of play which itallows, and its resistance to working loose. These characteristics areof particular importance in special instruments wherein the accuratecooperation of opposed operative means is required. This is the case,for example, with surgical clamping means having jaws specially designedto clamp tubular vessels of the body with the avoidance of damagethereto such as those described in US Pat. No. 3,608,554, issued Sept.28, 1971.

Heretofore, forceps and other surgical instruments having box lockjoints were typically made by producing aligned holes in the two membersto be joined, inserting a temporary pin, performing the necessarybending operations as well as grinding and polishing operations,removing the temporary pin, punching the holes in the bifurcated portionof the first member to a square or star configuration, hardening thefirst and second members, inserting a second pin, swaging or peening thepin, and finally finishing the instrument. Swaging of the pin followinghardening results in the setting up of stresses in the instrument whichremain unrelieved when the instrument goes into use. When the instrumentis subjected to the influences of superheated steam (autoclaving),repeated mechanical loads under surgical conditions, and corrosioncaused by the various elements in the surgical environment, thesestresses eventually, if not in a very short time, manifest themselves ascracks in and around the box lock joint.

Instrument breakage often occurs at the location of these cracks, andcan constitute a serious safety hazard if it takes place during surgery.

In some cases, the hinge pin is inserted and swaged prior to hardening.However, peening is sometimes required to tighten the pin when shrinkageoccurs in the hardening process. This peening results in stressessimilar to those which occur when the pin is swaged following hardening.The danger of breakage therefore exists in instruments made by thisalternative method.

The hinge pin itself is also susceptible to breakage. Although it is nota common occurence, if a hinge pin in a conventional instrument breaks,it is possible for a part of the pin to fall out of the instrument whilein use. In surgery, such an occurrence also represents a serious hazardto the patients safety.

In accordance with this invention, a pin having a head slightly largerthan the holes in the member having the bifurcated portion is insertedinto the aligned holes in the two members. The pin is electrically fusedin two steps, and thereby secured to the two separate elements of thebifurcated portion, there being a circular zone of fusion in each of thetwo separate elements having a penetration depth desirable between andpercent and preferably 100 percent. Fusion preferably takes place in aninert gas environment. The outer surfaces of the two separate elementsof the bifurcated portion are ground and polished, and the pin becomesinvisible. Hardening takes place after electric fusion. The processproduces a substantially stress-free box lock joint which is much lesslikely to fail in use than box lock joints made in accordance withconventional methods. In addition, if the hinge pin fractures, it isprevented from falling out of the instrument by the fact that it isfused to the elements of the bifurcated portion of the first member.

The principal object of the invention, therefore, is to provide asubstantially stress-free box lock joint having greater durability thanconventional box lock joints. A second object of the invention is toinsure against the loss of the hinge pin or parts thereof in the eventof hinge pin breakage. Further objects of the invention include thesimplification of the manufacturing process and the production of a boxlock joint having as little play as possible. Still other objects willbe apparent from the following detailed description when read inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a'perspective view of a boxlock clamp in accordance with the invention;

FIG. 2 is a partially cut away side elevation of a square punched boxlock joint in accordance with the prior art;

FIG. 3 is a bottom plan view of the joint of FIG. 2

FIG. 4 is a partially cut away side elevation of a star punched box lockjoint in accordance with the prior art;

FIG. 5 is a bottom plan view of the joint of FIG. 4;

FIGS. 6 through 9 are vertical sections taken through a box lock jointin accordance with the invention, illustrating the successive steps ofmanufacture;

FIG. 10 is a perspective view of a fixture used in the manufacture of abox lock surgical instrument in accordance with the invention; and

FIG. 11 is a vertical section of the fixture of FIG. 10.

DETAILED DESCRIPTION In FIG! 1, a box lock surgical clamp generallyindicated at 12 comprises a pair of members 14 and 16 joined together bya box lock joint generally designated 18. A jaw 20 on member 14 isarranged to cooperate with jaw 22 on member 16. Movement of the jawstoward and away from each other is controlled by manipulable rings 24and 26. Latching means adapted to set the jaws in any desired one of anumber of discrete positions comprise ratchet 28 and cooperating tooth30 respectively on members 14 and 16.

Member 14 has a bifurcated portion at the location of the joint wherebyjaw and ring 24 are connected by two separate elements 32 and 34 havingbetween them a slot 36. Internally, slot 26 has substantially flat,parallel sides. A portion 38 of member 16, machined to conform with theflat inner surfaces of slot 36 extends through the slot with jaw 22 andring 26 on opposite sides of the bifurcated portion of member 14. Ahinge pin (not shown in FIG. 1) extends across the interior of the slotand through a hole in element 38. The hinge pin allows the jaws to becontrolled by the manipulation of rings 24 and 26.

As described thus far, the instrument is entirely conventional. Inmanufacture in accordance with conventional methods, forged memberscorresponding to members 14 and 16 of the finished product are joined byspreading apart the elements corresponding to elements 32 and 34 ofmember 14, inserting member 16 between those elements, and bringingelements 32 and 34 back to their normal relationship. A hole is drilledthrough the elements corresponding to elements 34, 38 and 32, and atemporary pin is inserted to keep the parts in alignment duringformation of the jaws and other necessary bending and machiningoperations. The temporary pin is then removed, and the memberscorresponding to members 32 and 34 are punched to a square configurationas shown in FIG. 3, or to a multiple-point or star configuration asshown in FIG. 5. The elements of the instrument are then hardened, andthe final hinge pin is inserted and swaged into place. Followingswaging, final finishing of the instrument takes place. FIGS. 2, 3, 4and 5 illustrate two box lock joints in accordance with the prior art.In FIG. 2, it will be noted that the pin 40 is held in place only byreason of the fact that the swaging step widens its ends to fill thesquare configuration of the holes in the outer elements of the joint.This is also the case in FIG. 4 in which the ends of pin 42 are swagedto fill the sixpointed star configuration of the holes in the outerelements of the joint. In either case, the pin depends on its ownintegrity to hold it in place. Should it break by reason of a materialfailure transverse to the longitudinal axis, the pin could fall into thepatient during an operation. As previously stated, the box lock joint,as illustrated in FIGS. 2, 3, 4 and 5 is subject to breakage by reasonof the stresses produced by the swaging operation.

FIGS. 6, 7, 8 and 9 illustrate successive steps in the production of thefused box lock joint in accordance with the invention. As shown in FIG.6, a pin 44 having a head 46 is inserted into aligned holes in theelements of the box lock joint, the inner element being designated 48,and the outer elements being designated 50 and 52. The head 46 is largerin diameter than the hole in element 50, and the pin is thus retainedfor the first fusing operation.

FIG. 7 illustrates the result of the first fusing operation. The head istransformed into a weld 54 which securely fastens pin 44 to element 50of the joint. Weld 54 has a 100 percent depth of penetration in element50. This is not difficult to achieve, and optimum fusion time for agiven size of instrument can be easily determined. When a 100 percentdepth is reached, there is a considerably time lag before the currenttends to weld element 50 to element 48. Thus, there is considerableleeway in the range of fusion time which will produce a good weld withpercent penetration depth.

Following the first fusion step, the instrument is turned upside down,and a second fusion step takes place which fuses the protruding end ofpin 44 to element 52, producing a weld 56, as shown in FIG. 8, which issimilar to weld 54.

Finally, the excess fused material is ground away, and the instrument issubjected to any necessary final finishing steps and polishing. Thefinal operations produce smooth surfaces 58 and 60, as shown in FIG. 9.The pin is invisible. Except for the fact that the pin is invisible, theinstrument made in accordance with the invention resembles conventionalinstruments.

Preferably, a special fixture, such as that shown in FIGS. 10 and 11, isused for the drilling and fusion operations in accordance with theinvention. The fixture comprises a base 62 on which are mountedspecially shaped clamps including fixed clamps 64 and 66 and slidableclamps 68 and 70. The clamps hold the elements of the instrumentsecurely in a fixed position as shown for drilling of the aligned holes.Base 62, as shown in FIG. 11, is provided with a depression 72 fordrilling and also in order to accommodate the protruding end of the pin.The base is mounted on gearing including gear 74 and pinion 76 forrotation of the base during fusion to insure a uniform weld. Anelectrode 78 is shown in FIGS. 10 and 11 in position just above the Byway of specific example, a DeBakey ring handle bulldog clamp having anoverall length of about 5 inches and consisting of 410 stainless steelis assembled in accordance with the invention using a headed 0.075 inchdiameter, 0.195 inch long pin, also of 410 stainless. The instrument isdrilled to 0.078 inches. Fusion takes place at 32 amperes for 12 secondswith the electrode centered above the pin and spaced 0.037 inches fromthe head of the pin. The base is rotated at 10 rpm so that it rotatesthrough two complete revolutions during each fusing step. The foregoingproduces a 100 percent weld on each side of the box lock joint withoutfusing the elements of the box lock joint together.

A DeBakey angled straight jaw peripheral vascular clamp having anoverall length of 7 inches, a pin length of 0.230 inches and a pindiameter of 0.090 inches and otherwise similar to the above-mentionedbulldog clamp is assembled under the same conditions as listed above,except that the instrument is drilled to 0.093 inches and a current of35 amperes is used.

A 10 inch DeBakey tangential occlusion clamp having a pin length of0.271 inches and a pin diameter of 0.093 inches, and otherwise similarto the abovementioned clamps is assembled under the same conditions asthe above-mentioned vascular clamp except that the fusion current is setat 38 amperes.

Heavier instruments are assembled by the use of a longer fusing time, ora heavier fusing current, or both, and smaller instruments are assembledusing a shorter time or a lighter fusing current. The requiredconditions can be easily determined for any given instrument.Furthermore, the nature of the process allows for the production ofuniform 100 percent welds with a large margin of error in fusingconditions.

The process produces an exceptionally strong and reliable box lockjoint. Since no swaging of the pin takes place, the stresses whichresulted in failures of prior art instruments are not set up.Furthermore, since hardening takes place following fusion, any stresseswhich are present as a result of bending or machining or fusing stepsare relieved in the process of hardening the instrument. In addition,since the hinge pin is secured by fusing to the outer elements of thebox lock joint, it is prevented from falling out of the instrument evenif it is broken in use.

We claim: 1. The method of making a box lock surgical instrumentcomprising the steps of:

providing first and second members, the first member having a bifurcatedportion at an intermediate location whereby its ends are connected bytwo separate elements having a slot between them;

forming first and second aligned holes respectively in said separateelements of the first member and a third hole in an intermediate portionof said second member, the third hole alignable with the holes in thefirst member when said intermediate portion of the second member ispositioned in the slot between said separable elements;

with the intermediate portion of the second member positioned in saidslot, aligning the third hole with the first and second holes;

inserting a pin through said first, second and third holes;

electrically fusing said pin at one end to one of the separate elementsof the first member for a sufficiently long period of time to produce aweld having a 75 to 100 percent depth of penetration in said one of theseparate elements;

electrically fusing said pin at its other end to the other of theseparate elements of the first member for a sufficiently long period oftime to produce a weld having a 75 to 100 percent depth of penetrationin said other of the separate elements;

grinding the outside surfaces of the separate elements of the firstmember to remove excess material resulting from the fusing steps; and

hardening said instrument.

2. The method according to claim 1 in which the pin is provided with ahead sufficiently large to prevent its passing through the holes of saidseparate elements.

3. The method according to claim 1 in which the instrument is rotated ina plane transverse to the axis of the aligned holes during fusion.

4. The method of making a box lock surgical instrument comprising thesteps of:

providing first and second members, the first member having a bifurcatedportion at an intermediate location whereby its ends are connected bytwo separate elements having a slot between them;

forming, in a single drilling operation, first and second aligned holesrespectively in said separate elements of the first member and a thirdhole in an intermediate portion of said second member, the third holebeing alignable with the holes in the first member when saidintermediate portion of the second member is positioned in the slotbetween said separable elements;

with the intermediate portion of the second member positioned in saidslot, aligning the third hole with the first and second holes;

inserting a pin through said first, second and third holes;

fusing said pin at one end to one of the separate elements of the firstmember;

fusing said pin at its other end to the other of the separate elementsof the first member;

grinding the outside surfaces of the separate elements of the firstmember to remove excess material resulting from the fusing steps; and

hardening said instrument.

5. The method of claim 4 in which the drilling and fusion steps arecarried out while the instrument is mounted on a fixture.

6. The method of claim 4 in which the drilling and fusion steps arecarried out while the instrument is mounted on a fixture rotatable in aplane transverse to the axis of drilling and in which rotation of saidfixture takes place during the fusion steps.

1. The method of making a box lock surgical instrument comprising thesteps of: providing first and second members, the first member having abifurcated portion at an intermediate location whereby its ends areconnected by two separate elements having a slot between them; formingfirst and second aligned holes respectively in said separate elements ofthe first member and a third hole in an intermediate portion of saidsecond member, the third hole alignable with the holes in the firstmember when saId intermediate portion of the second member is positionedin the slot between said separable elements; with the intermediateportion of the second member positioned in said slot, aligning the thirdhole with the first and second holes; inserting a pin through saidfirst, second and third holes; electrically fusing said pin at one endto one of the separate elements of the first member for a sufficientlylong period of time to produce a weld having a 75 to 100 percent depthof penetration in said one of the separate elements; electrically fusingsaid pin at its other end to the other of the separate elements of thefirst member for a sufficiently long period of time to produce a weldhaving a 75 to 100 percent depth of penetration in said other of theseparate elements; grinding the outside surfaces of the separateelements of the first member to remove excess material resulting fromthe fusing steps; and hardening said instrument.
 2. The method accordingto claim 1 in which the pin is provided with a head sufficiently largeto prevent its passing through the holes of said separate elements. 3.The method according to claim 1 in which the instrument is rotated in aplane transverse to the axis of the aligned holes during fusion.
 4. Themethod of making a box lock surgical instrument comprising the steps of:providing first and second members, the first member having a bifurcatedportion at an intermediate location whereby its ends are connected bytwo separate elements having a slot between them; forming, in a singledrilling operation, first and second aligned holes respectively in saidseparate elements of the first member and a third hole in anintermediate portion of said second member, the third hole beingalignable with the holes in the first member when said intermediateportion of the second member is positioned in the slot between saidseparable elements; with the intermediate portion of the second memberpositioned in said slot, aligning the third hole with the first andsecond holes; inserting a pin through said first, second and thirdholes; fusing said pin at one end to one of the separate elements of thefirst member; fusing said pin at its other end to the other of theseparate elements of the first member; grinding the outside surfaces ofthe separate elements of the first member to remove excess materialresulting from the fusing steps; and hardening said instrument.
 5. Themethod of claim 4 in which the drilling and fusion steps are carried outwhile the instrument is mounted on a fixture.
 6. The method of claim 4in which the drilling and fusion steps are carried out while theinstrument is mounted on a fixture rotatable in a plane transverse tothe axis of drilling and in which rotation of said fixture takes placeduring the fusion steps.